It’s normal in flower for lower leaves to yellow off. Well… it’s not a horrible issue you’d have to rush & tend to. From the pic tho it does look like a potassium deficiency maybe. Only the big leaves were yellowing throughout the plant from what it seems.
Edit: I seen you’re all done with it now… but this was just for future reference.
I hear ya. Made a lot of mistakes on this first grow but ultimately very successful and happy w the outcome. Learned a lot, here and elsewhere, so thanks to anyone who gave input. Immediately started my second and it’s crazy how well it’s going in the early stages knowing now what to be looking for and a better idea of how to do it